Corrections to the Mann et al (1998) Proxy Data Base and Northern Hemisphere Average Temperature Series

Frequently Asked Questions (and Answers)

Who paid for this research?

No one. We neither sought nor received
financial support for this project.

Was your article peer-reviewed?

Yes. Our article was read by numerous
colleagues in Canada, the US, Australia and Europe, including experts in mathematics
and statistics, geology, paleoclimatology, climatology and physics.
It was refereed for Environment and Energy by reviewers selected
by the editor.

If there were all the errors in Mann et al (1998) that you allege, how could it have passed peer review for a
prestigious journal like Nature?

You would have to ask Nature about the
steps taken by their peer reviewers to verify the results in Mann et al.
(1998). However, a peer review is not an audit. It is extremely unlikely
that the peer reviewers for Nature even requested the original MBH
dataset, much less that they carried out the quality control tests that we
carried out.

How can a third party decide whether you are right or Mann et al. are right?

We have created an
audit trail so that
third parties can verify these findings for themselves. This includes what
we think is the first Internet posting of the original proxy data used in
Mann et al (1998). Some of the points are very easy to verify. To verify
the collation errors resulting in duplication of 1980 entries in the data,
one needs only inspect a few numbers. We’ve created excerpts from the data
and directions to the exact locations in the original data base. Anyone
can check this. Similarly, we’ve created excerpts and pointers in the
data base so that anyone can verify the extrapolations and “fills” merely
by inspection. To verifying that the MBH data base contains obsolete data,
we’ve made graphs to show the differences between the MBH versions and the
updated version in every case found (so far); we’ve also included data
files showing both versions together and URLs for the updated data. Anyone
can check this for themselves. We’ve included computer scripts in R, which
will collect the data from the URL site and make the graphs. Verifying the
principal components calculations is more work, but we’ve also made the
tools available to do this. We’ve provided collated data files for the
underlying tree ring series as well as descriptions of how to collect the
data. We’ve provided computer scripts showing our principal component
calculations and the explained variance using MBH principal components.
We’ve also provided a collated version of all the data and scripts for how
we replicated the MBH reconstruction. We believe that audit trails are
extremely important for this type of analysis and that the Internet
provides an ideal mechanism for ensuring public accessibility to such
audit trails.

Why didn't the IPCC pick up these errors?

You’d have to ask them. IPCC have not
described what measures of due diligence they carried out. One would
surmise that they did not carry out the type of data quality control tests
that we did. We understand that Mann was a lead chapter author and, in his
IPCC capacity, may not have carried out any due diligence on his own work.

Why has no one else picked up these errors?

Our guess is that no one else ever
examined the data in detail. MBH never placed the compilation at the WorldDataCenter for
Paleoclimatology or at their own FTP sites, as one might have expected. [Nov 4/03: This is not correct. An FTP site was
identified in the responses to our paper. It is ftp://holocene.evsc.virginia.edu/pub/MBH98/.]
[Nov 11/03 The previous correction was premature. See this update
for some further comments on FTP disclosure. Professor Mann has asserted that the data we analyzed was not the data
behind MBH98. But it turns out to be identical to what was on the ftp site. So either we did audit the right data or
the MBH98 data still haven't been FTP-posted.]
When Prof. Mann arranged for the data to be provided in April 2003, it was
not immediately available and it’s possible that no one ever requested it
before.

What led you to request the data from Prof. Mann?

McIntyre has a background in the mineral
exploration business. He wanted to see the underlying proxies (before any
statistical manipulations by Mann et al.) for exactly the same reason that
mining engineers want to look at drill cores in calculating ore reserves.
He had seen other proxy data which did not suggest that proxies were
behaving differently in the late 20th century. He had also seen
comments by Briffa that tree ring proxies had declined in the second half
of the 20th century and, since MBH data was heavily based on
tree rings, wondered how this was reflected in the MBH data. Since he was
unable to locate the data in a public archive, he requested it from Prof.
Mann.

Did you show this paper to Prof. Mann or ask Prof. Mann for comments prior to publication?

In late September 2003, we asked Prof.
Mann for additional information on his reconstruction methodology. Prof
Mann advised us that he was unable to provide us with such additional
information and would be unable to respond to further inquiries, owing to
the numerous demands on his time.

Are you qualified to verify this data?

Ultimately, to borrow a phrase, “the
proof is in the pudding”. If we’ve identified material errors and defects
in this data base, this would prove that we were qualified to do so. As a
more detailed answer, both of us have strong backgrounds in handling data
and in assessing data quality. McIntyre’s intuition that the data should
be examined like drill core shows that the practical experience and
scepticism that one acquires in the mineral exploration industry was not
misplaced here. Moreover, the paper is about statistical and “accounting”
issues, both of which are well within our ranges of experience and
competence. While McIntyre’s background is more on the practical side and McKitrick’s
more on the academic side, both have strong mathematical
skills and statistical training.

Do you have any ties to the energy sector or anti-Kyoto think tanks?

McKitrick is a Senior Fellow of the
Fraser Institute, a Canadian policy think tank that has taken a stand
against Kyoto. McIntyre
has worked many years in the mineral exploration industry. McIntyre is a shareholder
of a micro-capital energy exploration company, CGX Energy, has acted in
the past as a consultant to CGX and sub-leases office space from CGX. CGX
is not a producing company and, as a company, has no views on Kyoto and has provided no financial support
to this study.

Your graph seems to show that the 15th
Century was warmer than today’s climate: is this
what you are
claiming?

No. We’re saying that Mann et al., based
on their methodology and corrected data, cannot claim that the 20th
century is warmer than the 15th century – the nuance is a
little different. To make a positive claim that the 15th
century was warmer than the late 20th century would require an
endorsement of both the methodology and the common interpretation of the
results which we are neither qualified nor inclined to offer.

What led you to publish in E&E rather than Nature?

After receiving the MBH98 data from Scott Rutherford and Michael Mann, McIntyre posted a series of observations about curiosa in the
data on the
internet discussion group climateskeptics. Sonja Boehmer-Christiansen invited McIntyre to consider writing up his work for submission
and McIntyre agreed. Subsequent to this, McKitrick joined with McIntyre in the analysis and preparation of an article. McKitrick
suggested that an article be submitted to Nature and a 1500-word version (to fit the word limit in Nature) was drafted. But after
showing it to some scientific colleagues who were not familiar with the issue, we were advised that it
was too short a format to
convey the scope of the argument. So we chose to write a longer paper first in order to get the full body of
material out. It has been suggested to us that we write a letter to Nature summarizing what is spelled out in the longer paper and
we are considering this.

What if someone comes along and finds
errors in your work?

We've made it as easy as possible for them
to do so. We’ve displayed all our data and all our methods. We welcome the
scrutiny.

How closely did you replicate the original MBH98 results using the data they supplied you?

As we state in the paper we achieved substantial success in replication, but some differences
remained between their results and ours. We were unable to obtain advice from them on either data questions or methdology questions,
so we carried on with the rest of our analysis. Figure 6 in our paper shows the comparison of their temperature PC1 and
ours. The comparison of the final NH index versions looks very similar to that between the PC1 versions:
In their reply (see above) MB&H can also obtain a large variation in the 15th century, similar to ours, by making some changes that
approximate some of the changes between our versions.